The elucidation of the role of fibrinolysis in the regulation of tissue repair is continued. The influence of the special conditions prevailing in the vessel wall on the repair process and on the development of arterial disease is studied. The process of vascularization during repair is studied by the histochemical fibrin slide technique. Purification of the tissue plasminogen activator is continued and immune serum is prepared from highly purified preparations. Improved assay methods for determining blood fibrinolytic activity are developed. The process of glass-activation of blood fibrinolytic activity is studied and compared with the activation induced by anionic compounds. The diurnal increase in fibrinolytic activity in normal persons and in patients with hyperlipoproteinemia is compared with that produced by glass-activation in an effort to determine a possible correlation. Studies on experimental thrombolysis are continued. Studies on the effect of EACA on the activation of various forms of plasminogen are being completed.